1. Field of the Invention
The present invention relates to an LED (light-emitting diode) apparatus formed by collecting a plurality of LED elements to be capable of using as various illumination light sources.
2. Description of the Related Art
Conventional LED elements which are compound semiconductors have widely been utilized as light source devices, using characteristics of a long service life and miniaturization. Manufacturing light source devices to emit light of white color or pseudo white color has been promoted with development of blue-LED elements formed by gallium nitride-system-compound semiconductors and so on. In addition, light source devices having high output and high brightness in which heat-release of LED elements is devised have been manufactured.
On the other hand, because there is a limitation to light intensity in one LED element, there have been disclosed collecting-type LEDs or LED light-source units capable of obtaining much light intensity by mounting a plurality of LED elements on one substrate and lighting these LED elements (for reference, see Japanese Patent Application Publication No. 2006-295085 (page 3 of the specification and FIG. 1).
FIG. 18 illustrates a conventional typical LED light-source unit 100. The LED light-source unit 100 includes an elongate insulative substrate 101, a plurality of LED elements 110 arranged on a surface of the insulative substrate 101 in line at intervals in a longitudinal direction of the substrate, and a metallic plate and so on (not shown) fixed to another surface of the insulative substrate 101. The insulative substrate 101 has at opposite sides thereof two electrode terminals 102a and 102b. Electrodes 104 are formed to extend from the electrode terminals 102a and 102b along an array of the LED elements 110. Connection electrodes 103a and 103b are provided on the electrodes 104 adjacent to each of the LED elements 110.
Each of the plurality of LED elements 110 is connected through wires 111 to the adjacent connection electrodes 103a and 103b. Thereby, the LED elements 110 are connected parallel to the electrode terminals 102a and 102b. When a drive voltage is applied to the electrode terminals 102a and 102b, a drive current flows in each of the LED elements 110, all the LED elements 110 are concurrently lighted. The LED elements 110 are sealed by a seal member 105 so that they are electrically and mechanically protected.
In the conventional LED light-source unit, because the plurality of LED elements can be arranged in a manner of array and lighted simultaneously, it is possible to acquire a relatively great light intensity. In addition, in the conventional LED light-source unit, it is shown that various types of light sources can easily be formed by arranging a plurality of light-source units in a line state or dimensionally.
However, in the aforementioned conventional LED light-source unit, because the LED elements are arranged in line, and a light-emitting area has an elongate rectangular shape, there is a problem that an optical design is difficult for the fact that light emitted from the LED elements must be collected. Alternatively, if approximately a square light-emitting area is formed by arranging a plurality of LED light-source units, an easy optical design is obtained. However, because a gap tends to occur between the plurality of LED light-source units which are separate, increasing density of mounting the LED elements is difficult, there is a limitation to acquire a light-source device having high lumen-density (all light-flux density).
Here, in a general light source, if it has high lumen-density, the light source is very effective to perform an optical design such as a lens and so on for collecting emitted light, and an excellent light source having high output, high brightness and high light-emitting efficiency can easily be accomplished. Therefore, a light-source device having high lumen-density as various light sources for illumination are increasingly needed.